Oscillating middle axle for a utility vehicle

ABSTRACT

A utility vehicle is provided with a middle axle that is mounted at the end of a bogey beam for both flotational and oscillatory movement relative to the frame of the vehicle. The middle axle is restrained longitudinally by support links that are pivotally connected to the frame at a location that is forward of the rear drive axle. The middle axle is formed by a pair of stub axles interconnected by a support beam that is pivotally connected to the rearward end of the bogey beam. Vertical movement of the middle axle support wheels results in a corresponding vertical movement of the rearward end of the bogey beam and a rotation of the support beam about its pivotal connection on the bogey beam. The oscillatory movement is accomplished by a pivotal connection via a ball joint between a central support bracket mounting the transverse support beam to the longitudinally extending bogey beam.

FIELD OF THE INVENTION

[0001] The present invention relates generally to off-road motorvehicles, such as utility or recreational vehicles, and moreparticularly, to a middle axle apparatus for a utility vehicle toprovide oscillatory movement for the middle axle.

BACKGROUND OF THE INVENTION

[0002] Small off-road vehicles such as utility or recreational vehiclesare becoming popular for recreational and other general purpose off-roadusage. Such utility vehicles can be found in U.S. Pat. No. 4,706,770.These utility vehicles have found usage on golf courses and at sportingevents, and are particularly adaptable for utilization on a farm. Thistype of flexibility in the wide variety of uses necessitates a vehiclethat is highly flexible, highly maneuverable and the like. This demandsa vehicle that will afford a high degree of maneuverability and ease ofsteering.

[0003] Steering characteristics of known utility vehicles provide poorturning performance. Known utility vehicles have turning clearancecircles having a diameter greater than twenty-one feet. The use ofindependent front wheel suspension mechanisms on known utility vehicles,coupled with the mounting of the rack and pinion systems on the frame ofthe vehicle, introduces minor king pin rotations as the steering tiresride over ground undulations. Such construction reduces steeringprecision and can accelerate the wear of the tires on the steering axle.

[0004] Placing a load on the utility vehicle typically results in avariation in the steering performance of known utility vehicles. Forexample, one known embodiment having a front steering axle, a rear driveaxle, and a middle drive axle carries the load placed on the vehicle onthe middle and rear axles, resulting in proportionately less weight onthe steering axle and a reduction in maneuverability. Accordingly, knownutility vehicle construction results in a significant influence on thesteering performance by the load carried on the vehicle. Preferably,loads should not change the steering characteristics for any vehicle.

[0005] Furthermore, conventional utility vehicle construction mounts themiddle axle directly to the frame of the vehicle, resulting in a harshride characteristic and direct application of any load placed into theload bed onto the middle axle as well as the rear drive axle.Furthermore, the middle axle, in being fixed to the frame, is incapableof oscillatory movement, i.e. movement from side-to-side about alongitudinally extending pivot axis, which would further enhance theride characteristics of the utility vehicle. It would, therefore, bedesirable to enhance the ride characteristics, as well as the steeringperformance of utility vehicles by distributing the weight of the loadsbeing carried in a different manner and by providing a mechanismpermitting the middle axle to oscillate to better follow groundundulations.

[0006] It is therefor desirable to provide a utility and recreationalvehicle that overcomes the disadvantages of the known prior art utilityvehicles.

SUMMARY OF THE INVENTION

[0007] Accordingly, an important object of the present invention is toprovide a middle axle support apparatus for a utility vehicle that isnot directly mounted to the frame of the vehicle.

[0008] It is another object of this invention to provide a supportmechanism for the middle axle on a utility vehicle to provideflotational and oscillatory movement of the middle axle relative to theframe.

[0009] It is a further object of this invention to provide support forthe middle axle of a utility vehicle in such a manner as to prevent theload placed thereon from overcoming the steering operation of the frontaxle.

[0010] It is a feature of this invention to add a bogey beam extendinglongitudinally at the center line of the utility vehicle to interconnectthe front and middle axles.

[0011] It is another feature of this invention that a portion of theload placed into the load bed of the utility vehicle will be distributedto the bogey beam to be re-distributed to the front and middle axles ina predetermined proportion.

[0012] It is an advantage of this invention that maneuverability of theutility vehicle is greatly increased during load bearing operations.

[0013] It is a another advantage of this invention that the middle axleprovides the ability to oscillate and float relative to the frame of theutility vehicle.

[0014] It is still another advantage of this invention that the ridecharacteristics of a utility vehicle are improved, particularly underload bearing conditions.

[0015] It is still another feature of this invention that the loadsplaced on the load bed of the utility vehicle are proportionallydistributed between the front steering axle and the middle drive axle ofthe utility vehicle.

[0016] It is a yet another advantage of this invention that theflotational movement of the middle axle provides sufficient slack in thedrive mechanism to permit the chain drive to twist slightly in responseto the oscillation of the middle axle.

[0017] It is yet another feature of this invention that a centralsupport bracket pivotally connecting a support beam for the middle axleto the bogey beam allows a flotational movement of the middle axle withthe bogey beam and with longitudinally stabilizing support links.

[0018] It is a further object of this invention to provide a middle axlesupport mechanism for an off-road vehicle that is durable inconstruction, inexpensive to manufacture, carefree in maintenance, easyto assemble, and simple and effective in use.

[0019] These and other objects, features, and advantages areaccomplished according to the present invention by providing a utilityvehicle having a middle axle that is mounted at the end of a bogey beamfor both flotational and oscillatory movement relative to the frame ofthe vehicle. The middle axle is restrained longitudinally by supportlinks that are pivotally connected to the frame at a location that isforward of the rear drive axle. The middle axle is formed by a pair ofstub axles interconnected by a support beam that is pivotally connectedto the rearward end of the bogey beam. Vertical movement of the middleaxle support wheels results in a corresponding vertical movement of therearward end of the bogey beam and a rotation of the support beam aboutits pivotal connection on the bogey beam. The oscillatory movement isaccomplished by a pivotal connection via a ball joint between a centralsupport bracket mounting the transverse support beam to thelongitudinally extending bogey beam.

[0020] The foregoing and other objects, features, and advantages of theinvention will appear more fully hereinafter from a consideration of thedetailed description that follows, in conjunction with the accompanyingsheets of drawings. It is to be expressly understood, however, that thedrawings are for illustrative purposes and are not to be construed asdefining the limits of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The advantages of this invention will be apparent uponconsideration of the following detailed disclosure of the invention,especially when taken in conjunction with the accompanying drawingswherein:

[0022]FIG. 1 is side perspective view of a utility vehicle incorporatingthe principles of the present invention;

[0023]FIG. 2 is a top plan view of the utility vehicle of FIG. 1, theseats and control apparatus being shown in dashed lines, the frame andaxles being shown in phantom;

[0024]FIG. 3 is a top plan view of the frame and drive mechanism withthe chassis removed for purposes of clarity;

[0025]FIG. 4 is an enlarged cross-sectional view of the utility vehicletaken along lines 4-4 of FIG. 3 to show the drive mechanism and theorientation of the bogey beam supporting the front steering axle and themiddle drive axle;

[0026]FIG. 5 is an enlarged cross-sectional view of the utility vehicletaken along lines 5-5 of FIG. 3 to show an elevational view of themiddle drive axle;

[0027]FIG. 6 is an enlarged cross-sectional view similar to that of FIG.4 but showing flotational movement of the middle axle, the normalposition of the middle axle being shown in phantom; and

[0028]FIG. 7 is a top plan view of the frame and drive mechanism of analternative embodiment of the utility vehicle in which the engine andtransmission are mounted on a module that is partially supporteddirectly by the middle axle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Referring to FIGS. 1-3, a utility vehicle incorporating theprinciples of the present invention can best be seen. Any left and rightreferences are used as a matter of convenience and are determined bystanding at the rear of the vehicle and facing forwardly into thedirection of travel.

[0030] The utility vehicle 10 includes a frame 12 supported above theground G by a pair of steered wheels 22, 23 mounted on a front steeringaxle 20 and by a pair of driven wheels 25 mounted on a rear drive axle24. In the preferred embodiment depicted in FIGS. 1-3, a middle driveaxle 27 is also provided with a pair of opposing support wheels 28. Theframe 12 supports an operator compartment 13 including seats 14 for thecomfort of the operator and control apparatus, such as a conventionalsteering wheel 15 and a gear shift lever 16. A throttle control 17 and abrake control 18, along with other conventional control devices, arealso included within the operator compartment 13 for the control of thevehicle 10. The frame 12 also supports a load bed 19 rearwardly of theoperator compartment 13 over the middle and rear drive axles 27, 24respectively, to carry cargo over the surface of the ground G.

[0031] Referring now to FIG. 3, the frame 12 with the axles 20, 24, 27mounted thereon can best be seen. The rear drive axle 24 is rotatablysupported on the frame 12 and is powered by a drive mechanism 26 poweredby an engine 11 supported by the frame 12. The middle axle 27 ispivotally supported from the frame 12 by a pair of support links 29 andis connected to the rearward end of a bogey beam 30, which will bedescribed in greater detail below. The middle axle 27 is preferablyformed as a pair of stub shafts 27 a, 27 b connected to said respectivesupport links 29. A support beam 32 is pivotally mounted on a rearwardend of the bogey beam 30 for oscillatory movement about a longitudinallyextending pivot axis 33. The support wheels 28 on the middle axle 27 aredriven by respective chain drives 26 a to provide a four wheel drivecapability for the vehicle 10.

[0032] Front axle 20 and the mounting member 35 are attached to theforward end of the bogey beam 30, and, therefore, also pivot about axis33 a. The bogey beam 30 is pivotally connected to the frame 12 by apivot assembly 37 positioned beneath the operator compartment 13 toprovide an oscillation of the bogey beam 30 about the transverse pivotaxis 38. Accordingly, the front steering axle 20 and the middle axle 27generally oscillate in opposing vertical directions on opposite ends ofthe bogey beam 30 due to the pivotal mounting thereof by the pivotassembly 37.

[0033] The pivot assembly 37 can be formed as a simple pin assemblyconnecting the bogey beam 30 to the frame 12 of the vehicle 10 to definethe transverse pivot axis 38, as is shown in the drawings. The pivotassembly 37 can also suspend the bogey beam 30 from the frame 12 byproviding a link (not shown) that pivotally connects at one end to thebogey beam 30 and is centrally connected to the frame 12 with theopposing end of the link being connected to a spring mechanism (notshown) that provides some resiliency between the bogey beam 30 and theframe 12. Under such a suspended bogey beam arrangement, the transversepivot axis 38 would be located at the pivotal connection between thelink (not shown) and the bogey beam 30, but would be vertically movablerelative to the frame 12 about the pivotal connection between the link(not shown) and the frame 12, the spring mechanism (not shown)interconnecting the frame 12 and the link (not shown) to offset forcesencountered by the bogey beam 30. The location of the central pivot onthe link (not shown), pivotally connecting the link to the frame 12,being positioned between the opposing ends of the link to provide thedesired resiliency for the selected size of the spring mechanism.

[0034] Any load placed in the load bed 19 will be transferred to therear axle 24 through the mounting thereof with the frame 12 and to thebogey beam 30 via the pivot assembly 37. The weight carried by the bogeybeam 30 will be shared in a proportionate manner between the frontsteering axle 20 and the middle axle 27. The respective proportions willbe determined by the location of the pivot assembly 37 along a length ofthe bogey beam 30. Accordingly, any load transferred to the bogey beam30 will always be proportionately divided between the front steeringaxle 20 and the middle axle 27. As a result, the steeringcharacteristics will not be impacted by any load placed into the loadbed 19, as the middle axle 27 cannot overpower the front steering axle20.

[0035] The front steering axle 20 is operatively associated with asteering mechanism 40 to effect turning movement of the steered wheels22, 23. The steering mechanism 40 is actuated through manipulation ofthe steering wheel 15 by the operator through the universal connectinglinkage 42. The steering mechanism 40 includes a rack and pinionassembly 45 which includes a conventional pinion (not shown) rotatablyassociated with the steering wheel 15 and a conventional rack 47 that islinearly movable in conjunction with the rotation of the pinion 46 in aknown manner.

[0036] The rack 47 is pivotally connected to a first bell crank 50 at afirst connection point 48. The first bell crank 50 is pivotally mountedon the mounting member 35 for movement about a pivot 51. The connectionpoint 48 is positioned forwardly of the pivot 51 to effect pivotalmovement of the first bell crank. The right steered wheel 22 includes aspuckle 52 having a steering arm 53 extending rearwardly therefrom. Thefirst bell crank 50 is connected to the right steering arm 53 by asteering link 54 that extends laterally and rearwardly from the firstbell crank 50 to the rearward end of the steering arm 53.

[0037] The steering mechanism 40 also includes a second bell crank 55pivotally mounted on the mounting member 35 for movement about a pivot56. The second bell crank 55 is connected to the first bell crank 50 bya tie rod 60 for coordinated movement therebetween. Accordingly, pivotalmovement of the first bell crank 50 is transferred to the second bellcrank 55 through connection with the tie rod 60. The left steered wheel23 includes a spuckle 57 having a steering arm 58 extending rearwardlytherefrom. The second bell crank 55 is connected to the left steeringarm 58 by a steering link 59 that extends laterally and rearwardly fromthe second bell crank 55 to the rearward end of the steering arm 58.Accordingly, the left and right steered wheels 22, 23 are steered inconcert with one another in response to a manipulation of the steeringwheel 15 by the operator.

[0038] Referring now to FIGS. 3-5, the details of the bogey beamconstruction and the support of the middle drive axle 27 can best beseen. The support beam 32 at the rear end of the bogey beam 30 has thestub axles 27 a, 27 b mounted directly to the laterally opposing ends ofthe support beam 32. The support beam 32 further has a pair of mountingbrackets 34 projecting rearwardly therefrom interiorly of the stubshafts 27 a, 27 b to pivotally connect with the support links 29. Thesupport links 29 pivotally interconnect the frame 12 just forwardly ofthe rear drive axle 24 and the mounting brackets 34 on the support beam32. While the drawings depict the support links 29 connected to theframe 12 and the rear drive axle 24 fixed to the frame 12, analternative configuration can suspend the rear drive axle 24 from theframe 12 such that the rear drive axle 24 is vertically movable relativeto the frame 12. In such a configuration, the support links 29 wouldpreferably be mounted to the rear drive axle 24 to be vertically movabletherewith, but pivotable about an axis that is not coincidental with theaxis of the rear drive axle 24. Furthermore, the pivotal connectionbetween the support links 29 and either the frame 12 or the rear driveaxle 24 will be positionally adjustable in a for-and-aft direction toprovide for adjustment of the tension in the chain drive mechanism 26 a,as will be described in greater detail below.

[0039] The support beam 32 is also connected to a central supportbracket 31 which, in turn, is connected to the rearward end of the bogeybeam 30 by a ball joint 33 a defining the oscillation axis 33 whichpermits the middle axle 27 to oscillate about a longitudinally extendingaxis 33 to permit the middle axle 27 to follow ground undulations. Thecentral support bracket 31 also defines a pivotal connection between thebogey beam 30 and the support beam 32 such that the support beam 32which is fixed to the central support bracket 31 is free to pivot abouta bolt defining a transversely extending pivot axis 31 a that iseccentric with respect to the transverse axis of the middle axle 27.Accordingly, the middle axle 27 is capable of simultaneous pivotalmovement about the transverse axis 31 a and the pivotal connectionsbetween the support links 29 and the mounting brackets 34. Preferably,the pivotal connection between the support links 29 and the mountingbrackets 34 are in alignment with the stub shafts 27 a, 27 b definingthe middle axle 27. The transverse pivot axis 31 a is located below theline of the middle axle 27.

[0040] The pivotal connection of the support links 29 to the frame 12(or alternatively to the rear drive axle 24) is preferably formed as anassembly that is longitudinally movable to control the tension in thechain drive mechanism 26 a. With specific reference to FIG. 4, theposition of the support beam 32 on top of the bogey beam depicts theforwardmost adjustable movement of the support links 29. One skilled inthe art will readily recognize that a fore-and-aft movement of thesupport link 29 will cause pivotal movement of the support beam 32 aboutthe transverse pivot axis 31 a carried by the rearward end of the bogeybeam 30. Accordingly, the normal operative position of the support beam32 will be at an orientation above the bogey beam to allow for wearadjustment of the chain mechanism 26 a, similar to the solid linedepiction in FIG. 6.

[0041] In operation, as best seen in FIGS. 4-6, the middle axle 27 isfree to float or to oscillate with respect to frame 12 of the utilityvehicle 10. The vertical movement of the middle axle 27 duringflotational movement, or of even just one support wheel 28 during anoscillation movement, is accommodated by the pivotal connections of thesupport links 29, the bogey beam 30 and the support beam 32: The supportlinks 29 impose a controlled positional relationship with respect to themovements of the middle axle 27 relative to the rear drive axle 24, thuskeeping the chain drive mechanism 26 a in a proper drive transferringcondition. The support links 29 do not pivot on a center coincident withthe rear drive axle 24, but are pivoted at a point forwardly of the reardrive axle 24. Accordingly, the pivotal movement of the middle axle 27,as represented by the arc 29 a, will slightly shorten the distancebetween the middle axle 27 and the rear drive axle 24, thus allowing alittle slack in the chain drive mechanism 26 a to accommodate a slighttwisting of the chain drive mechanism 26 a when the middle axleoscillates about the ball joint 33 a. The floating movement of themiddle axle 27 about the rearward end of the support links 29, whosepivot axis is forward of the rear drive axle 24, will maintainacceptable tension in the chain drive mechanism 26 a for proper drivetransmission to the middle axle 27.

[0042] Furthermore, the middle axle 27 is mounted on the rearward end ofthe bogey beam 30 and any vertical floating movement of the middle axle27 must also move in conjunction with the limits imposed by the bogeybeam structure 30, as represented by the arc 30 a. Since the supportbeam 32 is pivotally connected to the rear end of the bogey beam 30 bythe central support bracket 31, the support beam 32 is capable ofpivoting rearwardly about the pivot axis 31 a, as represented by the arc32 a. Accordingly, the middle axle 27 vertically floats through pivotarcs 29 a, 30 a, and 32 a that coordinate to provide substantiallyvertical movement for the middle axle 27.

[0043] The vertical floating movement of the middle axle 27 is bestshown in FIG. 6. The normal position of the middle axle 27 is shown inphantom lines, while the raised position of the middle axle 27 toaccommodate a ground undulation is shown in solid lines. The verticalmovement of the middle axle 27 raises the rearward end of the bogey beam30, pivoting the bogey beam 30 about the front axle 20, and slightlyraises the operator compartment 13 as represented by the verticalmovement of the transverse pivot 38. The pivotal movement of the middleaxle 27 with respect to the support links 29 results in a correspondingpivotal movement of the central support bracket 31 about pivot axis 31a, causing the support beam 32 to raise above the bogey beam 30. Thisflotational capability of the middle axle 27 results in a smoother ridefor the operator than is known in the prior art construction with themiddle axle 27 fixed to the frame 12.

[0044] The downward vertical movement of the middle axle 27 results in asimilar operation of the pivot arcs 29 a, 30 a, and 32 a. The downwarddisplacement of the middle axle 27 moves the rearward end of the bogeybeam 30 downwardly along the arc 30 a. The fixed length of the supportlinks 29 results in a pivotal movement of the support beam 32 about thetransverse pivot axis 31 a, raising the support beam 32 relative to thebogey beam 30.

[0045] Referring now to FIG. 7, an alternative configuration of theutility vehicle can best be seen. The rear drive axle 24 carries asubstantially large portion of the weight of the vehicle 10 because ofthe direct mounting of the rear drive axle 24 to the frame 12. Themiddle axle 27, being supported from the rearward end of the bogey beam30, as is described in greater detail above, carries a significantlysmaller percentage of the vehicle load as compared to the rear axle 24.Some re-distribution of the vehicle weight can be accomplished accordingto the alternative embodiment shown in FIG. 7. Placement of the drivetrain components, such as the engine 11 and the transmission 11 a, on asupport module 65 that is at least partially carried by the middle axle27 would relieve the rear axle 24 of a significant portion of thevehicle load. Furthermore, this support module 65 would provide aconstant load on the middle axle 27 and would be accommodated by thebogey beam 30 to provide consistent ride and steering characteristics.

[0046] The support module 65 on which the engine 11 and transmission 11a are mounted is carried at the rearward portion thereof by a transversesupport link 69 connected to the opposing lateral sides of the frame 12.The connection between the support module 65 and the transverse supportlink 69 defines a transverse pivot axis to permit a relative pivotalmovement of the rearward end of the support module 65. The forward endof the support module 65 is carried directly by the middle axle 27, orby the support beam 32, so as to be weight bearing directly on themiddle axle 27. The support module 65 is preferably connected to thesupport beam 32 so as to be weight bearing on the middle axle 27. Theoperation of the support link 69 and the support module 65 forms asubstitute for the support links 29 described above with respect to theembodiment of FIGS. 1-6. Accordingly, the support module 65 is movablewith the middle axle 27 through both flotational and oscillatorymovements.

[0047] Preferably, in this alternative embodiment, the transmission 11 ais mounted on the support module 65 for direct driving connection withthe middle axle 27 so as to drive the support wheels 28 directly fromthe transmission 11 a. Drive to the opposing rear wheels 25 istransmitted via a pair of laterally opposed chain drives 26 a. Since therear axle 24 does not carry the weight of the engine 11 and transmission11 a, the rear axle 24 can be constructed as a pair of opposing stubshafts 24 a, 24 b that are directly mounted to the opposing sides of theframe 12. Preferably, the configuration of the support beam 32 with thepivoted central support bracket 31, as described in detail above, willbe utilized to provide both flotational and oscillatory movements of themiddle axle 27 relative to the frame 12.

[0048] The invention of this application has been described above bothgenerically and with regard to specific embodiments. Although theinvention has been set forth in what is believed to be the preferredembodiments, a wide variety of alternatives known to those of skill inthe art can be selected within the generic disclosure. The invention isnot otherwise limited, except for the recitation of the claims set forthbelow.

Having thus described the invention, what is claimed is:
 1. In a utilityvehicle having a frame supported by a steering axle having a pair ofsteered wheels pivotally mounted thereon, a drive axle mounted to theframe and having a pair of drive wheels mounted thereon, and a middleaxle having a pair of support wheels mounted at opposing ends thereof,the improvement comprising: a longitudinally extending bogey beampivotally connected to said frame and having a forward end connected tosaid steering axle and a rearward end; and a middle axle supportapparatus connected to said rearward end of said bogey beam andincluding: a transversely extending support beam pivotally connected tosaid rearward end of said bogey beam through a central support bracket,said support beam having opposing lateral ends supporting, respectively,said support wheels; a pair of support links pivotally connectedrespectively to laterally spaced mounting brackets on said support beam,said support links extending rearwardly from said support beam forpivotal connection to said frame; and a pivot member interconnectingsaid central support bracket and said bogey beam to define alongitudinally extending oscillation axis about which said support beamand said middle axis which is attached to said support beam oscillate tofollow ground undulations.
 2. The utility vehicle of claim 1, whereinsaid pivot member is a ball joint providing both said longitudinallyextending oscillation axis and a transverse pivot axis for movement ofsaid support beam relative to said bogey beam.
 3. The utility vehicle ofclaim 2, further comprising a drive mechanism connected with said middleaxle to transfer rotational power directly thereto, said rear drivewheels being rotatably driven from a drive transfer mechanism extendingrearwardly from said middle axle.
 4. The utility vehicle of claim 3,wherein said drive mechanism is mounted on a support module at leastpartially supported directly by said middle axle.
 5. The utility vehicleof claim 4, wherein said support links provide support for said supportmodule.
 6. The utility vehicle of claim 5, wherein said drive transfermechanism is a pair of, laterally opposed flexible drives transferringrotational power directly to the respective rear drive wheels.
 7. Theutility vehicle of claim 6, wherein said flexible drives are chaindrives.
 8. A utility vehicle comprising: a frame; a rear drive axlemounted to the frame and having a pair of drive wheels rotatablysupported thereon; a front steering axle having a pair of steered wheelspivotally mounted thereon; a middle axle having a pair of support wheelsmounted at opposing ends thereof; and a longitudinally extending bogeybeam pivotally connected to the frame and having a forward end and arearward end, said steering axle being connected to said forward end ofsaid bogey beam and said middle axle being connected to said rearwardend of said bogey beam; a support module mounted on said middle axle andextending rearwardly therefrom for connection to a support link mountedto said frame, said support module having a drive apparatus mountedthereon to provide operative driving power to said support wheels onsaid middle axle; and a drive mechanism interconnecting said supportwheels on said middle axle with said rear drive wheels to transferrotational power thereto.
 9. The utility vehicle of claim 8, furthercomprising a transversely extending support beam pivotally connected tosaid rearward end of said bogey beam through a central support bracket,said support beam having opposing lateral ends supporting respectivelysaid support wheels of said middle axle.
 10. The utility vehicle ofclaim 9, wherein said central support bracket is pivotally connected tosaid bogey beam by a pivot device that defines a longitudinallyextending oscillation axis about which said middle axle can oscillate tofollow ground contours.
 11. The utility vehicle of claim 10, whereinsaid pivot device is a ball joint.
 12. A utility vehicle comprising: aframe; a rear drive axle mounted to the frame and having a pair of drivewheels rotatably supported thereon; a front steering axle having a pairof steered wheels pivotally mounted thereon; a middle axle having a pairof support wheels mounted at opposing ends thereof; and a longitudinallyextending bogey beam pivotally connected to the frame and having aforward end and a rearward end, said steering axle being connected tosaid forward end of said bogey beam and said middle axle being connectedto said rearward end of said bogey beam via a transversely extendingsupport beam pivotally connected to said rearward end of said bogey beamby a pivot device that defines a longitudinally extending oscillationaxis about which said middle axle can oscillate to follow groundcontours; a support module mounted on said middle axle and extendingrearwardly therefrom for connection to a support link mounted to saidframe, said support module having a drive apparatus mounted thereon toprovide operative driving power to said support wheels on said middleaxle; and a drive mechanism interconnecting said support wheels on saidmiddle axle with said rear drive wheels to transfer rotational powerthereto.
 13. The utility vehicle of claim 12, wherein said centralsupport bracket defines a transverse pivot axis that is eccentric withan axis corresponding to said middle axle, said transversely extendingsupport beam is positioned above said rearward end of said bogey beam.14. The utility vehicle of claim 13, wherein said pivot device is a balljoint defining both said longitudinally extending oscillation axis andsaid transverse pivot axis to permit both Rotational and oscillatorymovements for said middle axle relative to said frame.